Field of the Invention
This invention relates to a method and apparatus for passing fluid flow through a section of a blade, for example, a blade of turbomachinery, turbines, rotating equipment and/or any other suitable or similar piece of equipment.
Discussion of Related Art
To improve efficiency, advanced gas turbines operate at temperatures that far exceed the allowable temperature of component materials. In order to maintain structural integrity and reasonable service life, cooling is needed for components of the engine that contact the hot gasses. Internal cooling, which should be efficient, effective, and uniform is difficult to accomplish throughout the entirety of the turbine. The particularly difficult areas to cool are the leading edges of the airfoils, the trailing edges of the airfoils, the endwalls that sandwich the blades and the vanes, and the blade tips.
The trailing edge, a particularly thin and vulnerable region, requires specific attention in the cooling process. Three main constraints increase the difficulties and challenges in cooling this region. First, the airfoil at this location is very thin, which leaves very little room or space for internal cooling designs without endangering structural integrity. Second, the amount of flow that exits the trailing edge should be minimized. Any flow extracted for internal cooling is not utilized directly for work, and thus represents an inherent loss in overall engine efficiency. It can be desirable to achieve enough of an increase in allowable turbine inlet temperature to offset the cost of coolant extraction. If large enough, the stream of coolant exiting the trailing edge may also disrupt the aerodynamics of the flow about the airfoil. Third, the pressure loss across the trailing edge must be carefully controlled, particularly so that upstream bleed holes operate correctly, while the blowing ratio at the outlet is maintained.
With conventional manufacturing processes, the production of the casting core for the trailing edge is relatively expensive and difficult. This is because the very small core must be machined to the complexity of the cooling geometry through drilling, milling, turning and grinding. These techniques lead to molded geometries that include pin fins, pedestals, ribs, and jet impingement areas. There have been numerous investigations studying the flow and heat transfer through these conventional geometries. Several conventional varied geometries have been investigated, each utilizing the aforementioned enhancement features in different configurations in order to create an increase in surface heat transfer as well as control pressure drop.
Recently, new manufacturing techniques have become available that allow for the production of much higher complexity casting cores without the restrictions of the traditional machining methods. In this way, new advanced cooling designs can be created in the thin geometry of the trailing edge. To date, very few of these advanced designs have been investigated for use in trailing edge cooling.